Question

How to replace every element in array by multiplication of next and previous elements with PHP

Answer 1

// arr[first] = arr[first] (itself) * arr[next];
// arr[last] = prev * arr[last] (itself);

function MultiplyNextPrevious(&$arr) {
    $size = count($arr);
    
    if ($size <= 1) {
        return;
    }
    
    $prev = $arr[0];
    $arr[0] = $arr[0] * $arr[1];
    
    for ($i = 1; $i < $size - 1; $i++) {
        $curr = $arr[$i];
        $arr[$i] = $prev * $arr[$i + 1]; // arr[i + 1] = next
        $prev = $curr;
    }
    $arr[$size - 1] = $prev * $arr[$size - 1];
}

$arr = array(2, 3, 5, 6, 12, 8, 10, 7);

MultiplyNextPrevious($arr);

for ($i = 0; $i < count($arr); $i++) {
    echo $arr[$i] . " ";
}




/*
run:

6 10 18 60 48 120 56 70 

*/

 

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